Many of us have seen films containing remarkably realistic dinosaurs, aliens, animated toys and other fanciful creatures. Such animations are made possible by computer graphics. Using such techniques, a computer graphics artist can specify how each object should look and how it should change in appearance over time, and a computer then models the objects and displays them on a display such as your television or a computer screen. The computer takes care of performing the many tasks required to make sure that each part of the displayed image is colored and shaped just right based on the position and orientation of each object in a scene, the direction in which light seems to strike each object, the surface texture of each object, and other factors.
Because computer graphics generation is complex, computer-generated three-dimensional graphics just a few years ago were mostly limited to expensive specialized flight simulators, high-end graphics workstations and supercomputers. The public saw some of the images generated by these computer systems in movies and expensive television advertisements, but most of us couldn't actually interact with the computers doing the graphics generation. All this has changed with the availability of relatively inexpensive 3D graphics platforms such as, for example, the Nintendo 64® and various 3D graphics cards now available for personal computers. It is now possible to interact with exciting 3D animations and simulations on relatively inexpensive computer graphics systems in your home or office.
A problem graphics system designers confronted in the past was how to provide a control interface for a graphics system that enables fast, efficient and flexible use of the graphics system by applications designed to be executed thereon. Various application programming interfaces (APIs) and application binary interfaces (ABIs) have been developed in the past for the purpose of enabling graphics application programmers to control the operation of a graphics chip provided in a graphics system. Perhaps the most commonly-used 3D graphics application programming interfaces in current use are Microsoft's Direct3D interface and the OpenGL interface developed through cooperation with Silicon Graphics. See, for example, Kovach, Inside Direct3D: The Definitive Guide to Real-Time 3D Power and Performance for Microsoft Windows (Microsoft Press 2000); and Neider et al., OpenGL Programming Guide: The Official Guide to Learning OpenGL Release 1 (Addison-Wesley Publishing Co. 1993).
As explained in the Kovach book, Microsoft's DirectX application programming interface (API) provides a set of interfaces offering efficient control of multimedia hardware on a computer running Microsoft Windows. Kovach states that DirectX lets programmers work with commands and data structures that are very close to those that the hardware can natively process, without being so low level that code has to be written differently for each device. By writing device-independent code, programmers can create software that will theoretically always perform at its best (according to Kovach)—even as users enhance their systems with new and improved 3D graphics accelerators, sound cards, input devices and other system capabilities.
Kovach explains that the device-independence of DirectX is obtained because the DirectX APIs are built on a hardware abstraction layer (HAL) that hides the device-specific dependencies of the hardware. In fact, DirectX defines some hardware acceleration support features that aren't available on much of the hardware built today in order to provide extensibility for the future.
While the DirectX approach has been widely adopted and is successful in providing compatibility across a wide range of different platform configurations, the use of a thick hardware abstraction layer and associated hardware emulation layer is not particularly suitable for current low cost dedicated video game platforms at the current time. The DirectX API was primarily designed for personal computers costing many hundreds or thousands of dollars and manufactured in a variety of different configurations and permutations. While the DirectX API has been successful in providing compatibility across a wide range of such different platform configurations, this compatibility has come at the expense of efficiency and performance. In the context of a dedicated low-cost video game platform, it is possible to do much better in terms of providing a fully capable programming interface that is very close to the hardware while providing a highly capable and flexible interface for achieving a wide variety of interesting 3-dimensional graphics effects.
One prior approach is described in U.S. patent application Ser. No. 08/990,133 filed Dec. 12, 1997 by Van Hook et al., entitled “Interface For A High Performance Low Cost Video Game System With Coprocessor Providing High Speed Efficient 3D Graphics And Digital Audio Signal Processing.” However, further improvements are possible and desirable. In particular, some people criticized the interface described in this prior Van Hook et al., patent application because they thought it was difficult to write applications to. In the home video game arena, it is desirable to maximize performance while keeping the interface used to invoke and control such performance and capabilities as simple and easy to use as possible. Requiring application programmers to write to an unduly complicated interface may increase the time it takes to develop such applications. This can have devastatingly negative effects when it comes time to launch a new video game platform—since the success of the platform may often depend on achieving a certain “critical mass” in terms of the number of games or other applications available at launch time. As some developers of prior new home video game platforms found out, no one wants to buy a new video game system if there are no games to play on it. It is therefore desirable to provide a graphics programming interface that is simple and easy to use and yet is very powerful and flexible.
The present invention solves this problem by providing new and improved interface for graphics systems that is designed to be as thin as possible in order to achieve high performance, while also providing a logical and orthogonal view of the graphics hardware.
The present invention provides a graphics system programming interface with graphics commands allowing geometry to be rendered with many attributes. The interface provides two main methods for drawing geometry. An immediate mode allows the command stream source to send a stream of graphics commands directly to the graphics processor for consumption. This immediate mode interface is useful when the main processor must synthesize geometry data from a higher-level description (e.g., a height field or Bezier patch). The second method feeds a command stream to the graphics processor using a memory-resident display list format. This interface provides superior performance for static data. The immediate interface and the display list interface both support configurable vertex representations. The configurable vertex representations include, for example, direct or indexed vertex components. Vertex components (e.g., position, normal, color and texture coordinates for a number of textures) can all be indexed independently from arrays, or placed directly in the command stream. Additional flexibility is provided by allowing each vertex component to have a differently-sized representation and precision. The available direct types may include, for example, 8-bit signed and unsigned integer, 16-bit signed and unsigned integer, and 32-bit floating point. A scale is available to position the decimal point for the integer types. The indirect types (e.g., 8-bit index or 16-bit index) can be used to index into an array of any of the direct types. This flexible representation allows the game developer to organize vertex data in a way that is appropriate for the game. The ability to index each component separately eliminates a great deal of data duplication.